Buddy at work on his Corolla has four different tires on it. Said he has been doing it for years. When he needs a new tire, goes to his tire guy and either gets a new or used tire.
The outer skins on those cars were a special plastic engineered and manufactured by Ashland Chemical / Polymers Div. You could bounce a bowling ball off of them and they wouldn't dent! the color is molded into the plastic "I Think". Like the Bricklin that Jay Leno just had a piece on.